Offset compensated baseline restoration and computationally efficient hybrid interpolation for the brain PET

Abstract

The acquisition of positron emission tomography (PET) pulses introduces artifacts and limits the performance of the scanner. To minimize these inadequacies, this work focuses on the design of an offset compensated digital baseline restorer (BLR) along with a two-stage hybrid interpolator. They respectively treat the incoming pulse offsets and limited temporal resolution and improve the scanner performance in terms of calculating depth of interactions and line of responses. The offset of incoming PET pulses is compensated by the BLR and then their interesting parts are selected. The selected signal portion is up-sampled with a hybrid interpolator. It is composed of an optimized weighted least-squares interpolator (WLSI) and a simplified linear interpolator. The processes of calibrating the WLSI coefficients and characterizing the BLR and the interpolator modules are described. The functionality of the proposed modules is verified with an experimental setup. Results have shown that the devised BLR effectively compensates a dynamic range of bipolar offsets. The signal selection process allows focusing only on the relevant signal part and avoids the unnecessary operations during the post-interpolation process. Additionally, the hybrid nature allows improving the signal temporal resolution with an appropriate precession at a reduced computational complexity compared to the mono-interpolation-based arithmetically complex counterparts. The component-level architectures of the BLR and the interpolator modules are also described. It promises an efficient integration of these modules in modern PET scanners while using standard and economical analog-to-digital converters and field-programmable gate arrays. It avoids the development of high-performance and expensive application-specific integrated circuits and results in a cost-effective realization.

Computationally Efficient Hybrid Interpolation and Baseline Restoration of the Brain-PET Pulses

“…The shape and amplitude of electrical pulses produced by photo-detectors enable undesirable interactions to be reduced [2,3,11,14]. In this context, sophisticated PET pulses readout and conditioning are used to maximally preserve this information [12][13][14][15].…”

“…PET pulses readout introduces artifacts [11,12,16]. It degrades the exactitude of measuring the PET pulses energies and timestamps [11].…”

“…It degrades the exactitude of measuring the PET pulses energies and timestamps [11]. It influences device consistency in calculating DOIs and LORs, which lowers the scanner's sensitivity and resolution [11,12,16]. BLRs, pile-up correctors, and high-precision timestamp calculators are being used to resolve these deficits [11,[16][17][18][19][20][21].…”

“…BLRs are utilized in this framework. Various BLRs have been suggested, ranging from analog approaches to adaptive solutions based on digital filters [11,12,[16][17][18][19][20][21].…”

“…Another primary method in PET scanners is the measurement of annihilation timestamps. It allows the collection of adequate annihilations to create LORs and also prevents the processing of ineffective information at IRM [11,12]. Various timestamp calculators were suggested for this purpose.…”